Three-Coordinate Iron(II) Dialkenyl Compound with NHC Ligation: Synthesis, Structure, and Reactivity

The reaction of [(IPr₂Me₂)₂FePh₂] with PhCCPh furnished a three-coordinate iron­(II) dialkenyl complex, [(IPr₂Me₂)­Fe­(σ-CPhCPh₂)₂] (<b>1</b>, IPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene), that represents a rare example of isolable low-coordinate iron alkenyl complexes with a high-spin ground state. Complex <b>1</b> was characterized by ¹H NMR spectroscopy, solution magnetic susceptibility measurement, Mössbauer spectroscopy, single-crystal X-ray diffraction study, and elemental analyses. A reactivity study revealed the reactions of <b>1</b> with PhCH₂Cl to produce cross-coupling product Ph₂CCPhCH₂Ph (<b>2</b>), with [Cp₂Fe]­[BAr^F₄] to yield Ph₂CCPh–CPhCPh₂ (<b>3</b>), and with CO, 2,6-dimethylphenyl isocyanide, and phenyl azide to produce novel iron(0) and iron­(II) complexes <b>4</b>–<b>6</b> bearing triphenylvinyl-derived ligands. These transformations demonstrated the high reactivity of the low-coordinate iron alkenyl complex

Three-Coordinate Cobalt(IV) and Cobalt(V) Imido Complexes with N‑Heterocyclic Carbene Ligation: Synthesis, Structure, and Their Distinct Reactivity in C–H Bond Amination

The reaction of the cobalt(0) alkene complex [(IMes)­Co­(η²:η²-dvtms)] (<b>1</b>) (IMes = 1,3-bis­(1′,3′,5′-trimethylphenyl)­imidazol-2-ylidene, dvtms = divinyltetramethyldisiloxane) with 2 equiv of DippN₃ (Dipp = 2,6-diisopropylphenyl) afforded the cobalt­(IV) imido complex [(IMes)­Co­(NDipp)₂] (<b>2</b>), which could be oxidized by [Cp₂Fe]­[BAr^F₄] (Ar^F = 3,5-di­(trifluoromethyl)­phenyl) to give the cobalt­(V) imido species [(IMes)­Co­(NDipp)₂]­[BAr^F₄] (<b>3</b>). The molecular structures of all these complexes were established by single-crystal X-ray diffraction studies. Characterization data and theoretical calculations suggest ground spin states of <i>S</i> = ¹/₂ and <i>S</i> = 0 for the cobalt­(IV) and cobalt­(V) species, respectively. When heated, the cobalt­(IV) imido species was converted to a cobalt­(II) diamido complex via an intramolecular C–H bond amination reaction, but the cobalt­(V) species was stable under similar conditions. The different outcomes suggest that a high oxidation state does not guarantee C–H bond activation reactivity of late-transition-metal imido species

Selective Double Carbomagnesiation of Internal Alkynes Catalyzed by Iron-N-Heterocyclic Carbene Complexes: A Convenient Method to Highly Substituted 1,3-Dienyl Magnesium Reagents

Controlled multicarbometalation of alkynes has been envisaged as an efficient synthetic method for dienyl and polyenyl metal reagents, but an effective catalyst enabling the transformation has remained elusive. Herein, we report that an iron­(II)-N-heterocyclic carbene (NHC) complex (IEt₂Me₂)₂FeCl₂ (IEt₂Me₂ = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene) can serve as a precatalyst for the double carbometalation of internal unsymmetrical alkynes with alkyl Grignard reagents, producing highly substituted 1,3-dienyl magnesium reagents with high regio- and stereoselectivity. Mechanistic studies suggest the involvement of low-coordinate organoiron­(II)-NHC species as the in-cycle intermediates. The strong σ-donating nature of IEt₂Me₂ and its appropriate steric property are thought the key factors endowing the iron-NHC catalyst fine performance

Three-Coordinate Iron(II) Dialkenyl Compound with NHC Ligation: Synthesis, Structure, and Reactivity

The reaction of [(IPr₂Me₂)₂FePh₂] with PhCCPh furnished a three-coordinate iron­(II) dialkenyl complex, [(IPr₂Me₂)­Fe­(σ-CPhCPh₂)₂] (<b>1</b>, IPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene), that represents a rare example of isolable low-coordinate iron alkenyl complexes with a high-spin ground state. Complex <b>1</b> was characterized by ¹H NMR spectroscopy, solution magnetic susceptibility measurement, Mössbauer spectroscopy, single-crystal X-ray diffraction study, and elemental analyses. A reactivity study revealed the reactions of <b>1</b> with PhCH₂Cl to produce cross-coupling product Ph₂CCPhCH₂Ph (<b>2</b>), with [Cp₂Fe]­[BAr^F₄] to yield Ph₂CCPh–CPhCPh₂ (<b>3</b>), and with CO, 2,6-dimethylphenyl isocyanide, and phenyl azide to produce novel iron(0) and iron­(II) complexes <b>4</b>–<b>6</b> bearing triphenylvinyl-derived ligands. These transformations demonstrated the high reactivity of the low-coordinate iron alkenyl complex

Carbon–Carbon Bond Formation Reactivity of a Four-Coordinate NHC-Supported Iron(II) Phenyl Compound

The preparation and characterization of a NHC-coordinated (NHC = N-heterocyclic carbene) ferrous phenyl complex [(IPr₂Me₂)₂FePh₂] (<b>1</b>; IPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) as well as its C–C bond formation reactivity have been studied. The four-coordinate iron­(II) phenyl complex was prepared from the reaction of ferrous chloride with PhMgBr and IPr₂Me₂. It reacts with nonactivated primary and secondary alkyl bromides and chlorides to furnish cross-coupling products and the iron­(II) monophenyl species (IPr₂Me₂)₂FePhX (X = Br (<b>2</b>), Cl). When it is treated with cyclooctatetraene (cot) or [Cp₂Fe]­[BAr^F₄] in the presence of PMe₃, it undergoes coordination or one-electron oxidation induced reductive elimination of biphenyl to form the corresponding iron(0) or iron­(I) species [(IPr₂Me₂)₂Fe­(η⁴-cot)] (<b>3</b>) or [(IPr₂Me₂)₂Fe­(PMe₃)₂]­[BAr^F₄] (<b>4</b>). All of these iron-containing products have been fully characterized by various spectroscopic methods. Complex <b>1</b> and (IPr₂Me₂)₂FeCl₂ catalyze the reaction of <i>n</i>-C₈H₁₇Br with (<i>p</i>-tolyl)­MgBr to afford the cross-coupling product in moderate yields (49% and 47%), whereas the reactions employing <b>4</b> and <b>1</b>/PMe₃ as catalysts give the cross-coupling product in very low yields. The results reflect the complexity of the reaction mechanism of iron-catalyzed coupling reactions

Carbon–Carbon Bond Formation Reactivity of a Four-Coordinate NHC-Supported Iron(II) Phenyl Compound

The preparation and characterization of a NHC-coordinated (NHC = N-heterocyclic carbene) ferrous phenyl complex [(IPr₂Me₂)₂FePh₂] (<b>1</b>; IPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) as well as its C–C bond formation reactivity have been studied. The four-coordinate iron­(II) phenyl complex was prepared from the reaction of ferrous chloride with PhMgBr and IPr₂Me₂. It reacts with nonactivated primary and secondary alkyl bromides and chlorides to furnish cross-coupling products and the iron­(II) monophenyl species (IPr₂Me₂)₂FePhX (X = Br (<b>2</b>), Cl). When it is treated with cyclooctatetraene (cot) or [Cp₂Fe]­[BAr^F₄] in the presence of PMe₃, it undergoes coordination or one-electron oxidation induced reductive elimination of biphenyl to form the corresponding iron(0) or iron­(I) species [(IPr₂Me₂)₂Fe­(η⁴-cot)] (<b>3</b>) or [(IPr₂Me₂)₂Fe­(PMe₃)₂]­[BAr^F₄] (<b>4</b>). All of these iron-containing products have been fully characterized by various spectroscopic methods. Complex <b>1</b> and (IPr₂Me₂)₂FeCl₂ catalyze the reaction of <i>n</i>-C₈H₁₇Br with (<i>p</i>-tolyl)­MgBr to afford the cross-coupling product in moderate yields (49% and 47%), whereas the reactions employing <b>4</b> and <b>1</b>/PMe₃ as catalysts give the cross-coupling product in very low yields. The results reflect the complexity of the reaction mechanism of iron-catalyzed coupling reactions

Additional file 1: of IL-10/STAT3 is reduced in childhood obesity with hypertriglyceridemia and is related to triglyceride level in diet-induced obese rats

Table S1. mRNA expression in adipose tissue and serum levels of IL-10. (DOCX 17 kb

Four-Coordinate Iron(II) Diaryl Compounds with Monodentate <i>N</i>‑Heterocyclic Carbene Ligation: Synthesis, Characterization, and Their Tetrahedral-Square Planar Isomerization in Solution

The salt elimination reactions of (IPr₂Me₂)₂FeCl₂ (IPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with the corresponding aryl Grignard reagents afford [(IPr₂Me₂)₂FeAr₂] (Ar = Ph, <b>3</b>; C₆H₄-<i>p</i>-Me, <b>4</b>; C₆H₄-<i>p</i>-^<i>t</i>Bu, <b>5</b>; C₆H₃-3,5-(CF₃)₂, <b>6</b>) in good yields. X-ray crystallographic studies revealed the presence of both tetrahedral and trans square planar isomers for <b>3</b> and <b>6</b> and the tetrahedral structures for <b>4</b> and <b>5</b>. Magnetic susceptibility and ⁵⁷Fe Mössbauer spectrum measurements on the solid samples indicated the high-spin (<i>S</i> = 2) and intermediate-spin (<i>S</i> = 1) nature of the tetrahedral and square planar structures, respectively. Solution property studies, including solution magnetic susceptibility measurement, variable-temperature ¹H and ¹⁹F NMR, and absorption spectroscopy, on <b>3</b>–<b>6</b>, as well as an ⁵⁷Fe Mössbauer spectrum study on a frozen tetrahydrofuran solution of tetrahedral [(IPr₂Me₂)₂⁵⁷FePh₂] suggest the coexistence of tetrahedral and trans square planar structures in solution phase. Density functional theory calculations on (IPr₂Me₂)₂FePh₂ disclosed that the tetrahedral and trans square planar isomers are close in energy and that the geometry isomerization can occur by spin-change-coupled geometric transformation on four-coordinate iron­(II) center

Four-Coordinate Iron(II) Diaryl Compounds with Monodentate <i>N</i>‑Heterocyclic Carbene Ligation: Synthesis, Characterization, and Their Tetrahedral-Square Planar Isomerization in Solution

The salt elimination reactions of (IPr₂Me₂)₂FeCl₂ (IPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with the corresponding aryl Grignard reagents afford [(IPr₂Me₂)₂FeAr₂] (Ar = Ph, <b>3</b>; C₆H₄-<i>p</i>-Me, <b>4</b>; C₆H₄-<i>p</i>-^<i>t</i>Bu, <b>5</b>; C₆H₃-3,5-(CF₃)₂, <b>6</b>) in good yields. X-ray crystallographic studies revealed the presence of both tetrahedral and trans square planar isomers for <b>3</b> and <b>6</b> and the tetrahedral structures for <b>4</b> and <b>5</b>. Magnetic susceptibility and ⁵⁷Fe Mössbauer spectrum measurements on the solid samples indicated the high-spin (<i>S</i> = 2) and intermediate-spin (<i>S</i> = 1) nature of the tetrahedral and square planar structures, respectively. Solution property studies, including solution magnetic susceptibility measurement, variable-temperature ¹H and ¹⁹F NMR, and absorption spectroscopy, on <b>3</b>–<b>6</b>, as well as an ⁵⁷Fe Mössbauer spectrum study on a frozen tetrahydrofuran solution of tetrahedral [(IPr₂Me₂)₂⁵⁷FePh₂] suggest the coexistence of tetrahedral and trans square planar structures in solution phase. Density functional theory calculations on (IPr₂Me₂)₂FePh₂ disclosed that the tetrahedral and trans square planar isomers are close in energy and that the geometry isomerization can occur by spin-change-coupled geometric transformation on four-coordinate iron­(II) center